1. Field of the Invention
The present invention relates to a process for forming color photographic images, more particularly, to a process for forming color photographic images by a reversal color photographic process.
2. Description of the Prior Art
Reversal color photographic processes are well known in the art and are described in, for instance, C. E. K. Mees, "The Theory of the Photographic Process", 2nd ed., Chapter 25 (1954). Reversal color photographic materials processed by such reversal color processes are generally classified into two types. In one type silver halide emulsion layers contain couplers and in the other type the silver halide emulsion layers do not contain couplers.
A reversal color photographic process fundamentally comprises a first development step with a black and white developer, a second development step with a color developer, and a desilvering step. In more detail, when an exposed reversal color photographic material is developed in the first development step, the exposed portions of the color photographic material are blackened as a result of the development but the unexposed portions thereof remain substantially unchanged. In the second development step, the silver halide in the unexposed portions is color developed to form dye images and silver images, therein while in the exposed portions the proportion of the color images formed by the color development becomes lower in proportion to the degree of exposure since the silver halide in the photographic silver halide emulsion layers was consumed in the first development step and no color image is formed in portions sufficiently exposed. The color photographic material thus developed is then processed in a desilvering step, in which developed silver is oxidized by the action of an oxidizing agent (usually called a "bleaching agent") and the oxidized silver is dissolved off from the color photographic material by a fixing agent or a silver halide complexing solvent. Thus, positive dye images are formed in the color photographic material.
The desilvering step usually comprises a bleach step and a fix step, or, alternatively, comprises a blix step (or bleach stabilization step) wherein bleaching and fixing (or stabilization) are performed simultaneously.
Processing reversal color photographic materials comprises the above-mentioned three fundamental steps, and, if desired or necessary, may further include such auxiliary steps as pre-hardening, film removal, neutralization, stopping, image stabilization, washing, etc., to retain the photographic and physical qualities of the color images, and to improve the stability of the images.
In color photography, the cleaness of the color, the fine granularity, and the sharpness of the image are fundamental and important factors for the quality of color images. Furthermore, it is desirable for color photographic films for photographic use that the photographic films have high sensitivity.
As one means for obtaining color images having fine granularity, a method is known in which the proportion of silver halide in the photographic silver halide emulsion layers is increased (see U.S. Pat. No. 2,689,793). This method, however, is accompanied by the disadvantage that the density of the dye images formed by color development greatly increases to give a hard gradation to overcome this disadvantage, it is known to incorporate competing couplers in a color developer.
The above-mentioned method of increasing the proportion of silver halide is also further accompanied by another drawback in that when this technique is applied to the upper layer or layers of multilayer color photographic materials, the sharpness of the color images formed in a lower layer or layers is decreased due to increased light scattering. As a means for overcoming this drawback, a method has been provided in which the proportion of silver halide in the photographic emulsion layer forming a yellow dye image the granularity of which is visually less sensitive is reduced and the emulsion layer is disposed as the upper layer of the color photographic material. However, when a color photographic material having such a photographic emulsion layer is developed in a color developer containing a competing coupler as indicated above, the color images formed in the yellow dye forming emulsion layer show greatly reduced density and gradation.